Switching circuit



March .2, 1954 Filed July 19, 1950 R. S. NORTON SWITCHING CIRCUIT 2Sheets-Sheet 1 INVENTOR. Ha/p/Y .5. Norton March 2, 1954 s, NORTON2,671,169

SWITCHING CIRCUIT Filed July 19, 1950 V 2 Sheets-Sheet 2 BY I fizzyPatented Mar. 2, 1954 Ralph StNorton,

Sperry Corporation,

corporation of Delaw Brooklyn, N. Y., assignor to The Long Island City,N. Y., a are Application July 19, 1950, Serial No. 174,621

a Claims. (01. 250-27) This invention relates to an electronic-switching circuit and more circuitfor use in a multiple speed servo mechanismin which a plurality of signals are to be applied selectively to actuatethe mechanism.

In one embodiment the invention may be applied to a. servo mechanism inwhich the primary control is from a fine control signal, a secondarycontrol is exerted by a coarse control signal'which is superimposed onthe fine control signal when the coarse control signal exceeds apredetermined value, and a tertiary control is effected by a secondcoarse control signal which is connected to remove the firstcoarsecontrol signal and to be superimposed on the fine control signal in lieuthereof.

An object of the invention is to provide a novel and improved system ofthe above type.

Another object is to provide a system which operates with a low noiselevel.

Another object is above type which is accurate and dependable inoperation.

particularly to a switching" to provide a system of the Various otherobjects and advantageswill be apparent as the nature of the invention ismore fully disclosed. r

' The invention will be better understood by referring to the followingdescription, taken in connection with the accompanying drawings in 1which certain specific embodiments thereof have been set forth forpurposes of illustration.-

in the drawings; 7 Fig. 1 is a schematic diagram of an electronicswitching system embodying the present inven-' tion; and

Fig. 2 is a similar trating a further embodiment of the invention.

Referring to the drawings more in detail, Fig. l

schematic diagram illusshcws a system in which the input signal E1 isapplied to input terminals l0 and H,- the latter being grounded.Terminal through a condenser R2 to the of a gas tube l3, the positive isconnected by a lead [4 to the of a triode iii. The lead a resistor I7and condenser negative terminal of the gas to the anode of a rectifierdiode 20, the cathode negative terminal to a terminal 23 which isconnectedto a source of positive potential B2. the triode 25 is alsoconnected through a resistor terminal of which control grid 15 Itisgrounded through I8 in parallel. The tube I 3 is connected 7 40 I 0 isconnected 1 The control grid 24 of 1 In the operation of this device analternating input signal E1 is supplied to the input terminals in and H.When the voltage on the terminal l0 swings positive the tube 20 conductscurrent. If this voltage is less than the breakdown voltage of the gastube I3 when a positive voltage is applied to a negative terminal, thegas tube I3 will not conduct. Therefore capacitor l2 will store a chargeduring this half cycle with the voltage at point 59 going negative.During the next half cycle of the input signal, as the input term nalii! goes negative the rectifier 20 will not conduct. Consequently thepoint I9 is now negative by an value of'the input signal. If the voltageat the point 19 is now less than the breakdown voltage of the gas tubel3 when a negative voltage is applied to its negative terminal, the gastube will not break down. During the next half cycle in the positivedirection, since the point i9 is already positive by an amount equalto'the peak value of the input signal no current will flow through therectifier 2!] except that necessary to compensate for any charge thatmay have leaked off of the condenser l2. Similarly, the gas tube l3cannot break down.

is at a voltage less than the breakdown voltage of the gas tube 13 thegrid l5 of the triode I6 is near ground potential. Since the cathode 22of the'tube I6 is grounded, the tube It tends to draw 7 a large platecurrent. If the resistor 30 is large the plate potential of the tube It,which is also the control grid potential of the tube 25, is at apotential very near ground. Since the cathode When breakdown occurs thegas tube l3 conducts and a negative bias the tube I'S. thus out 01f isapplied to the grid I 5 of and allows the plate voltage of the tube 15,and the grid voltage on the control grid amount approximately twice thepeak As long as the point l9 Consequently the gas'tube The plate currentof the tube It is of the tube 25, to return to a value of B2. The tubethen conducts since B1 is greater than B2, and the input signal appliedthrough the condenser 3i to the grid 24 of the tube 25 is amplified andappears at the output terminal as an amplified output voltage. The timeconstants of the resistor H and condenser I8 must be large compared tothe period of the input voltage so that the grid potential of the triodeit never rises above its cut-off value while the gas tube 13 isconducting. The time constant must also be small enough to have littleefiect on the servo mechanism response characteristic;

It is evident from the above that the: output signal across theterminals 35. and 36' is a function of the input signal across theterminals 10 and II when the input signal exceeds a predetermined value,but is cut oil sharply when the input signal falls below saidpredetermined value. Hence if the terminals 35 and 36 are connected to aservo control mechanism which is supplied with a fine control signal andthe coarse control signal is applied across the terminals Ill and H,then the coarse signal is effectively cut off from the output terminals35 and 36 when it is below its predetermined value. Above this value thecoarse control signal appears at the output terminals and issuperimposed on the fine control signal oi the servo mechanism. Belowthe cutoff point the system operates with an extremely small noiselevel.

In Fig. Zthe invention is shown as applied to a switching arrangementfor selectively applying either of two input signals to theoutputterminals.- For convenience and to simplify the description the'parts ofFig. 2 corresponding to the above described parts of Fig. 1 have beengiven the same: reference characters and operate in the same manner.

In. Fig. 2 an amplifier tube 48 has been connected between the inputterminal l5 and the condenser 12 so as to make the system responsive tosmaller input signals.

The amplifier tube 40 is provided with a con-- trol grid 4| connected tothe input terminal I9 and with an anode 12 which is connected to thecondenser 12 and also through a resistor 43 to the B1 terminal 3d. Thecathode 44 of the amplifier tube fit is grounded through resistor 45.

InFig. 2 the diode 25 in Fig. 1 has been replaced by a triode 59. Thetriod has an anode 5| connected to the negative terminal of gas tube i3,and a grounded cathode 52.

The second input signal E2 is applied across terminals and 51, thelatter being grounded. The terminal 53 is connected to the control grid5310f. a triode 59 having a cathode grounded through-a resistor 61, andan anode 62 connected through a condenser 63 to the negative terminal ofa gas tube 3d, and connected through a resistor 55 and lead 55 to the B1terminal 34.

A diode 10 is provided with an anode ll which is connected to thenegative terminal of gas tube 56 anda grounded cathode l2.

The positive terminal 15 of gas tube 64 is connected by a lead it to thecontrol grid 11 of a triod 18. The lead It is grounded through aresistor '39 and condenser in. parallel. The triode i8 has a groundedcathode 84 and an anode 85 connected by a lead 86 to the control grid 81of a triode 88, and also through a lead 89 and condenser 90 to the inputterminal 56. The lead 16 is also connected by a lead 54 to the controlgrid 53 of the triode 5B. The control grids? of the triode 8B is alsoconnected through a resistor 93, lead 94 and resistor 95 to the lead 66.The lead 94 is also grounded through a resistor 91. The cathode 98 ofthe triode 88 is connected through a resistor 99 to the lead 94.

The anode I95 of the triode 88 is connected through a resistor 106 tothe lead 56 and through a condenser I01 and lead 108 to the outputterminal 35, also through a resistor I09 to ground. The anode 32 of thetriode 25 is connected through a condenser H0 to the lead I08.

When the voltage on the grid 53 or the triode 50 is at ground potentialthe triode 50 acts in a manner similar to the diode 20 of Fig. 1 and thetriode 25 passes the input signal E 1 supplied from the input terminal"[0, provided this signal exceeds the value necessary to unblock thetriode 25 as. described in connection with Fig. 1. The amplifier tube 19serves to amplify th input signal atthe. terminals l0 and II so thatcontrol may take place at a much lower value of signal than could beobtained-by the circuit of Fig. l.

The amplifier tube 40 is also designed so that its amplified signal doesnot exceed a prede-- termined value of swing because of saturationandcutoff.

The peak value of the voltage on plate 42 is limited by this means toapproximately three quarters of the breakdown voltage of gas tubel3.When triode 50 is out off by the voltage on itsgrid 53 goingsufficiently negative, the voltage onplate 5| cannot exceedthree-quarters of thebrealrdown voltage of tube l3. Therefore the gastube l3 cannot be made to conduct or sustain conduction. Consequentlythe circuit has been disabled.

The second channel carrying the second input signalEz across theterminals 58 and 51 is similar to the first channel above mentioned andoperates in a similar way. The signal is amplified by the amplifier tubecondenser 53m the gas tube 54 and, due to the diode 10' whichcorresponds to the diode 20 of Fig. 1, causes the gas tube 64 to conductsignal reachesa predetermined value. With the gas. tube 641'non-conducting the grid ll of the triode "i8 is of the same potential asits cathode 84 and the tube 18 draws current, thereby making thecontrolgridSl of the triode 88 sufficiently negative. to cut off triode88.

Now when the second. input voltage E2 reaches a sufii'cient value tocause the gas tube 54 to be-- come conducting a negative voltage isapplied to the line 15, thence to the grid ll of the triode i8, cuttingofi the tube l8. This negative voltage is also applied through the lead5 3 to the grid 55 of the triode 59, thereby rendering the tubeflinch-conducting and cutting off the con-' trol signal E1 from thefirst channel as above pointed out. When the tube 78 is cut on thevoltage on the grid 8? of the triode 38 becomes positive and the triode-88 becomes conductive. and amplifies the second input signal which issupplied thereto from: theoutput circuit of the amplifier tube 59. Thissignal is accordingly applied to the output terminals 35 and 36 in placeof the amplified signal from the input terminals lit and H.

t is evident from the above that if a' first coarse control signal isapplied to the input terminals ill and H and a second coarse controlsignal is applied to the input terminals 56 and 51, and thexoutputterminals 35 and 33 are connected to a servo mechanismnormallyresponsive to a fine control. signal, then no voltage will be applied.across the output terminals as long as 59, is applied across the whentheboth coarse input signals are below a predetermined value. However,as soon as the first input signal E1 across the terminals and II exceedsthis minimum value the first channel is rendered operative and theamplified input signal from the triode 25 is applied across the outputterminals 35 and 36 and is superimposed on the fine control signal ofthe servo mechanism. During this time the second channel is inoperativebecause the second coarse control signal is not suflicient to cause thegas tube 64 to conduct. As soon as the second coarse input signal E2across channel is blocked by reason of the blocking of the tube 56 andthe second channel is made operative to amplify the second coarse inputsignal and apply the same to the terminals 35 and 36 to be superimposedon the fine control signal of the servo mechanism.

While the above system has been shown as applied to control of amulti-speed servo, the system may be used for various purposes whereinthe output signal is to be made responsive to one of two input signalsdepending upon the values thereof. Hence various changes andmodifications may be made in the specific circuit disclosed as will bereadily apparent to a person skilled in the art.

What is claimed is:

1. An electronic control circuit comprising a pair of channels, each ofsaid channels containing an amplifier tube, an input circuit carrying acontrol signal connected to the input of said first amplifier tube, asecond input circuit carrying a second control signal connected to theinput of said second amplifier tube, means in each of said channelsnormally blocking the respective amplifier tubes, means in each of saidchannels responsive to the respective input signals and connected tounblock the respective tubes when the respective input signals exceedpredetermined values, and means in said second channel to block saidfirst channel when said second amplifier tube becomes unblocked, and asingle output circuit connected to the output of both of said amplifiertubes.

2. An electronic control circuit comprising a pair of channels, each ofsaid channels containing an amplifier tube, an input circuit carrying acontrol signal connected to the input of said first amplifier tube, asecond input circuit carrying a second control signal connected to theinput of said second amplifier tube, each of said input circuitsincluding a normally conducting triode connected to apply a blockingbias to the respective amplifier tube, and also a rectifier circuitincluding a rectifier tube and a gas tube connected to apply a blockingbias to the respective A triode when the rectified input voltage issulficient to cause the respective gas tube to conduct, and a connectionfrom said rectifier circuit of said second input circuit to apply ablocking bias to the rectifier tube of said first input circuit when thegas tube of said second input circuit becomes conducting.

3. An electronic control circuit comprising a pair of channels, each ofsaid channels containing an amplifier tube, an input circuit carrying acontrol signal connected to the input of said first amplifier tube, asecond input circuit carrying a second control signal connected to theinput of said second amplifier tube, each of said input circuitsincluding a normally conducting triode connected to apply a blockingbias to the respective amplifier tube, and also a rectifier circuitincluding a rectifier tube and a gas tube connected to apply a blockingbias to the respective triode when the rectified input voltage issufiioient to cause the respective gas tube to conduct, a connectionfrom said rectifier circuit of said second input circuit to apply ablocking bias to the rectifier tube of said first input circuit when thegas tube of said second input circuit becomes conducting, and a singleoutput circuit connected to the output of both of said amplifier tubes.

4. A circuit as set forth in claim 2 in which the rectifier tube of saidfirst input circuit is a triode and said connection supplies a blockingbias to the control grid thereof. 4

5. An electronic control circuit comprising an amplifier tube having acontrol grid, means supplying an input signal to said control grid foramplification by said tube, an output circuit connected to said tube toreceive said amplified signal, a triode connected to be normallyconducting and having an output circuit connected to apply a negativebias to said control grid of said amplifier tube for blocking the same,a rectifier circuit including a gas tube, a series condenser and a shuntrectifier connected to apply a blocking bias to said triode when therectified signal is suflicient to cause said gas tube to conduct, meansapplying said input signal to said rectifier circuit, and an outputcircuit connected to the output of said amplifier tube.

RALPH S. NORTON.

References Cited in the file of this patent UNITED STATES PATENTS

